A man dressed as Uncle Sam with a puppet of John Key has taken pride of place at an anti-spy rally in Marlborough.

Around 50 protesters have marched through Blenheim this morning, and many are picketing Waihopai Spy Base this afternoon.

The picket is largely centred on the Government's controversial ramping up of the powers of spy agency the GCSB.

Pickets have been carrying flags for the Green Party and Mana Movement and adapted American flags.